System and method for correcting spatial luminance variation of computed radiography image plates
A computed radiography plate including a substrate is provided. The computed radiography plate also includes at least one phosphor layer disposed above the substrate. The computed radiography plate also includes a protective layer disposed above the phosphor layer. The computed radiography plate further includes multiple patterns inscribed within at least one of the phosphor layer, the protective layer or the substrate.
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The invention relates generally to computed radiography, and more particularly, to correction of spatial luminance variation in computed radiography plates.
Typically, a computed radiography plate acts as a reusable X-ray image storage device. The computed radiography plate is initially exposed to X-ray radiation and placed into a reader for read-out and erasure. The plate is ready for a new X-ray exposure after erasure. During read-out of a computed radiography plate, an initial pixel array representing stored X-ray intensities over the plate must be corrected to account for various stationary, spatial variations in a structure of the plate and additional optical system variations. For example, the size of phosphor grains typically may be of a similar size as that of the pixel that leads to small variations in image intensity if uncorrected. Further, it is required to minimize structure noise to less than +/−0.1% of peak signal levels.
One of the commonly known correction techniques includes scanning a generic test plate exposed with a uniform X-ray radiation pattern and further using resultant array of values to produce a calibration image. The calibration image is used to compensate for large-scale grain noise and variation in optical transmission in a detection system. To achieve a highest signal-to-noise ratio in a range of greater than 200-300 to 1, detector elements need to be repositioned exactly each time a specific plate is read. Further, each detector pixel needs to be placed within a small fraction of a phosphor grain diameter.
However, it is not possible to passively mechanically align a plate relative to the detector elements to guarantee translation errors and rotational errors less than a desirable range due to large size and inherent flexibility of the plate. Moreover, most fixturing methods in use typically cause damage to a surface of the plate if improperly adjusted, thus limiting reuse of the plate.
Therefore, an improved system and method for correcting spatial luminance variation is desirable to address one or more of the aforementioned issues.
BRIEF DESCRIPTIONIn accordance with an embodiment of the invention, a computed radiography plate is provided. The computed radiography plate includes a substrate. The computed radiography plate also includes at least one phosphor layer disposed above the substrate. The computed radiography plate also includes a protective layer disposed above the phosphor layer. The computed radiography plate further includes multiple patterns inscribed in at least one of the phosphor layer or the protective layer or the substrate.
In accordance with another embodiment of the invention, a system for correcting luminance variation in a computed radiography plate is provided. The system includes a carriage configured to move along a length of the plate. The carriage includes one or more imaging detectors configured to move to predefined locations on a surface of the computed radiography plate. The carriage also includes one or more sensors configured to read a pattern on the plate and detect the error in position or orientation of the one or more imaging detectors relative to the pattern. The carriage further includes one or more actuators configured to adjust translation and angular orientation of the one or more imaging detectors in response to a signal from the one or more sensors. The system also includes a microprocessor coupled to the one or more detectors and the one or more actuators, the microprocessor being configured to store a calibration image of the computed radiography plate.
In accordance with another embodiment of the invention, a method for manufacturing a computed radiography plate is provided. The method includes disposing a substrate. The method also includes determining patterning of the substrate. The method further includes forming multiple patterns within or on the substrate based upon the determination. The method also includes disposing at least one phosphor layer on the substrate. The method also includes forming multiple patterns within or on the phosphor layer based upon the determination. The method also includes disposing a protective layer on the at least one phosphor layer. The method further includes determining patterning of the at least one protective layer. The method further includes forming a plurality of patterns within or on the protective layer based upon the determination.
In accordance with another embodiment of the invention, a method of patterning a computed radiography plate is provided. The method includes providing a computed radiography plate, wherein the computed radiography plate includes a substrate. The computed radiography plate also includes at least one phosphor layer disposed above the substrate. The computed radiography plate also includes a protective layer disposed above the phosphor layer. The computed radiography plate further includes multiple patterns inscribed within or on at least one of the phosphor layer or the protective layer or the substrate layer.
These and other advantages and features will be more readily understood from the following detailed description of preferred embodiments of the invention that is provided in connection with the accompanying drawings.
As discussed in detail below, embodiments of the invention include a system and method for correcting spatial luminance variation of computed radiography plates. The system and method provide a means to accurately position a reading array to a tolerance of at least less than one pixel during readout, by creating spatially-invariant fixed patterns that act as position encoder tracks, on the computed radiography plates.
A control system 52, including a control loop microprocessor 54 (
It should be noted that embodiments of the invention are not limited to any particular processor for performing the processing tasks of the invention. The term “microprocessor,” as that term is used herein, is intended to denote any machine capable of performing the calculations, or computations, necessary to perform the tasks of the invention. The term “microprocessor” is intended to denote any machine that is capable of accepting a structured input and of processing the input in accordance with prescribed rules to produce an output.
The resolution of the sensor 48 is governed by the size of the intersection of the areas of light incident on surface 116 from fiber 112 and the area of the field of view of fiber 114. In order to accurately measure position with sub-pixel accuracy, the sensitive area of sensor 48 is designed to be approximately equal to the pixel size on plate 10. As the field of view of the sensor 48 increases for a fixed pattern feature size, the ability to measure sub-pixel positions degrades. In another embodiment, the sensing function may be implemented using discrete optical emitters and imaging detectors along with suitable lenses and apertures without the use of optical fibers. In a particular embodiment, the discrete optical emitters and imaging detectors may be used in conjunction with lenses, apertures, phototransistors and light emitting diodes.
In one embodiment, the multiple patterns are formed via laser etching. In another embodiment, the multiple patterns are mechanically embossed. In yet another embodiment, a surface property such as, but not limited to, angular reflectivity, spectral reflectivity and polarization state of reflected light is modified to detect presence of the pattern. In an exemplary embodiment, the patterns are formed together after disposition of the substrate, the phosphor layer and the protective layer.
The various embodiments of a system and method for correcting spatial luminance variation in computed radiography plates described above thus provide a way to achieve high image quality at a reasonable cost. The system and method also eliminates read-out artifacts such as, but not limited to, streaks, banding commonly observed and with a signal to noise amplification by a factor of about 2 to about 10. Further, the system allows for detection of smaller flaws that cannot be commonly detected.
It is to be understood that not necessarily all such objects or advantages described above may be achieved in accordance with any particular embodiment. Thus, for example, those skilled in the art will recognize that the systems and techniques described herein may be embodied or carried out in a manner that achieves or optimizes one advantage or group of advantages as taught herein without necessarily achieving other objects or advantages as may be taught or suggested herein.
Furthermore, the skilled artisan will recognize the interchangeability of various features from different embodiments. For example, the use of a sensor with a polarization film with respect to one embodiment can be adapted for use with a computed radiography plate inscribed with a two dimensional grid pattern. Similarly, the various features described, as well as other known equivalents for each feature, can be mixed and matched by one of ordinary skill in this art to construct additional systems and techniques in accordance with principles of this disclosure.
While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.
Claims
1. A computed radiography plate comprising:
- a substrate;
- at least one phosphor layer disposed above the substrate;
- a protective layer disposed above the phosphor layer; and
- a plurality of patterns inscribed within or on the phosphor layer, and the protective layer, and the substrate.
2. The computed radiography plate of claim 1, wherein the phosphor layer comprises a flexible layer.
3. The computed radiography plate of claim 1, wherein the substrate or the protective layer comprises a plastic material.
4. The computed radiography plate of claim 1, wherein the phosphor layer comprises a thickness between about 0.1 mm to about 0.2 mm.
5. The computed radiography plate of claim 1, wherein the protective layer comprises a thickness between about 0.01 mm to about 0.02 mm.
6. The computed radiography plate of claim 1, wherein the patterns are configured to allow simultaneous measurement of translation and orientation error of an imaging detector with respect to an underlying image pixel grid.
7. A system for correcting luminance variation in a computed radiography plate comprising:
- a carriage configured to provide a relative motion along a length of the plate, the carriage comprising:
- one or more imaging detectors configured to move to predefined locations on a surface of the computed radiography plate, the detectors further configured to be sensitive to photo stimulated luminescence;
- one or more sensors configured to read a pattern on the plate and detect an error in a position or an orientation of the one or more detectors relative to the pattern, the sensors further configured to be insensitive to photo stimulated luminescence; and
- one or more actuators configured to adjust translation and angular orientation of the one or more detectors in response to a signal from the one or more sensors; and
- a microprocessor coupled to the one or more imaging detectors and the one or more actuators, the microprocessor being configured to store a calibration image of the computed radiography plate.
8. The system of claim 7, wherein the one or more imaging detectors comprise at least one of a linear array or a two dimensional array.
9. The system of claim 7, wherein the one or more sensors comprise at least one pair of optical fibers having a transmitting optical fiber and a receiving optical fiber, wherein the transmitting optical fiber is configured to deliver light and the receiving optical fiber is configured to receive reflected light from the surface of the computed radiography plate.
10. The system of claim 7, wherein the one or more sensors comprise a plurality of discrete optical elements.
11. The system of claim 10, wherein the plurality of discrete optical elements comprise lenses, apertures, phototransistors and light emitting diodes.
12. The system of claim 7, wherein the one or more actuators comprise micro-actuators.
13. The system of claim 7, wherein the one or more imaging detectors are configured to correct sub-pixel translation errors within a plurality of resolutions.
14. The system of claim 13, wherein the resolutions comprise 25 microns, 50 microns, and 100 microns.
15. The system of claim 9, comprising a radio frequency identification reader configured to retrieve the calibration image.
16. A method for manufacturing a computed radiography plate comprising:
- disposing a substrate;
- determining patterning of the substrate;
- forming a plurality of patterns within or on the substrate based upon the determination;
- disposing at least one phosphor layer on the substrate;
- determining patterning of the at least one phosphor layer;
- forming a plurality of patterns on the at least one phosphor layer based upon the determination;
- disposing a protective layer within or on the at least one phosphor layer;
- determining patterning of the at least one protective layer; and
- forming a plurality of patterns within or on the protective layer based upon the determination.
17. The method of claim 16, wherein the forming comprises laser etching the patterns.
18. The method of claim 16, wherein the forming comprises mechanical embossing the patterns.
19. The method of claim 16, wherein the forming comprises modifying a plurality of polarization properties of the patterns.
20. A method of patterning a computed radiography plate comprising:
- providing a computed radiography plate, comprising: a substrate; at least one phosphor layer on the substrate; and a protective layer on the phosphor layer; and
- forming a plurality of patterns within or on the protective layer, and the phosphor layer, and the substrate.
21. The method of claim 20, wherein the forming comprises laser etching the patterns.
22. The method of claim 20, wherein the forming comprises mechanical embossing the patterns.
23. The method of claim 20, wherein the forming comprises modifying a plurality of polarization properties of the patterns.
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Type: Grant
Filed: Dec 10, 2007
Date of Patent: Apr 6, 2010
Patent Publication Number: 20090146079
Assignee: General Electric Company (Niskayuna, NY)
Inventors: Nelson Raymond Corby, Jr. (Scotia, NY), Clifford Bueno (Clifton Park, NY)
Primary Examiner: David P Porta
Assistant Examiner: Kiho Kim
Attorney: Joseph J. Christian
Application Number: 11/953,122
International Classification: H05B 33/00 (20060101);